1. Field of the Invention
The present invention relates to all-terrain vehicle (ATV) drive systems, and more specifically relates to differential joints for a rear transmission and to locking mechanisms for locking differential joints to universal joints of a vehicle transmission.
2. Related Art
Most powered vehicles with front end steering capabilities include some type of differential joint and an associated pair of universal joints, such as a constant velocity (CV) joints, positioned on opposing sides of the differential joint in a front end portion of the transmission assembly. A differential joint facilitates rotation of the opposing universal joints at different speeds. This feature is particularly useful when turning a vehicle because it facilitates a smaller turning radius with less friction resistance between the wheels and a surface over which the vehicle moves.
One disadvantage of differential joints is that they typically add additional width to the vehicle transmission and/or track. Transmission and track width are directly correlated with the clearance of the vehicle for a given wheel size and vehicle suspension and frame. In recreational vehicles, such as ATVs, it is often desirable to minimize the transmission and/or track width to improve vehicle clearance. For this and other reasons, there has not been an effective differential joint put into practice for an ATV rear-end transmission portion.
Many known vehicle drive systems are equipped with differential locking mechanisms to lock the differential and ensure that power from the vehicle engine is allocated to specified wheels of the vehicle. Although locking the differential may significantly reduce the turning capabilities of the vehicle, locking the differential makes it possible to allocate equal amounts of power to each wheel associated with that differential joint regardless of whether one of the wheels would normally spin freely (little or no traction for that wheel).
Differential locking mechanisms are typically positioned in the differential joint and between the opposing universal joints of a transmission. Such locking mechanisms are preferably adjustable from an unlocked to a locked position to control power allocation to the universal joints. One disadvantage of most locking mechanisms is that they tend to widen the vehicle transmission and/or track width. As discussed above, a wider transmission and/or track may have undesirable limitations in some applications. Another disadvantage of some locking mechanisms is their complexity in design and the inherent reworking of the transmission that is required to implement the locking mechanism into the transmission.